Dr. Abdul Kader Tabbara, a neurosurgery fellow at Boston Medical Center, was wrapping up appointments with patients in his clinic Monday afternoon when colleagues began streaming into the office, talking about explosions.

There was a lot of blood, they were saying. And a lot of wounded. And they were coming to his hospital.

Dr. Tabbara, a 28-year-old from Ann Arbor, Michigan, heard the sirens and went to the window: ambulances were lined up in front of the emergency room, and as quickly as one left, another arrived.

He made his way to the emergency room, his pager already thrumming.

“All the beds were taken. Stretchers were lining the walls. You could see surgeons from different teams waiting for the next victim to come in. Sheets were soaked with blood, patients were crying and screaming,” Dr. Tabbara said.

Seven of the 23 victims taken to the hospital from the scene of Monday’s Boston Marathon bombing arrived in critical condition, Peter Burke, the chief of Trauma at Boston Medical Center, said Tuesday, having sustained “multiple traumatic amputations, vascular injuries and some abdominal injuries.” Two patients lost both their legs, he said. As of Wednesday afternoon, 18 remained hospitalized and two were in critical condition, including a 5-year old boy who sustained severe lung damage.

Dr. Tabbara, the neurosurgeon, looked around and found his patient: a man in his early 20s on a stretcher, with blood covering his chest from a head wound. His hair smelled singed; the man had been on fire.

The man was a runner. He told Dr. Tabbara he had just finished the race and was waiting for a family member or a friend to finish when he was caught “very close” to the explosion. The man was knocked off his feet, and he got up and “just started to run, and he noticed his sweatshirt was on fire and he ripped that off,” Dr. Tabbara said.

The man didn’t stop running until he got to a medical tent, Dr. Tabbara said.

A brain scan showed the man had a complex laceration to his scalp, and a ball bearing embedded in his temple—but it hadn’t penetrated his skull. He had another ball bearing embedded in his nose.

Police officers sprang into action near a Boston Marathon runner.

The man was taken into surgery, where Dr. Tabbara scrubbed in and assisted another surgeon removing the ball bearing from the man’s temple. Dr. Tabbara said his phone rang and he asked a nurse to answer—it was Dr. Tabbara’s wife anxious to know if he was OK. “Tell her I’m OK,” Dr. Tabbara said he instructed the nurse.

Dr. Tabbara and the medical team cleaned the man’s head lacerations and removed the ball bearing from his temple. They left the operating room so a team of ear, nose and throat specialists could remove the ball bearing embedded in the man’s nose.

Dr. Tabbara then plunged back into the emergency room, helping where he could and checking on his patient, deep into the night.

More than 170 patients were treated at at least seven hospitals, some of them with minor injuries.

Paul Biddinger, chief of emergency preparedness at Massachusetts General Hospital, was part of the medical support team stationed at “heartbreak hill” near mile 20 of the marathon. As word of the bombings spread, he raced to the hospital and found the response well under way. Thirty patients who had been in the emergency department were transferred upstairs to make room for those wounded in the bombing. Trauma surgeons, orthopedic surgeons, nurses, respiratory therapists were standing by.

Two of the patients taken to Massachusetts General Hospital were near death. Their mangled legs were destroyed, with bones hanging by shreds of muscle and skin. Blood flowed profusely. Many had suffered massive wounds and burns.

Mass General says four of the patients remained in critical condition Wednesday, though none are expected to die.

Most of the patients were in shock, said Dr. George Velmahos, the hospital’s chief trauma surgeon. The hospital had to start amputating legs, completing four within a few hours. “Amputating wasn’t a hard decision,” Dr. Velmahos said.

Dr. Velmahos said the hospital—from its janitors to highest management—had prepared for such an event, with ample blood supply and materials for an influx of near-death patients. The hospital had finished trauma drills before with mannequins, and several of the doctors, including Dr. Velmahos, have worked in war-torn countries.

Dr. Alasdair Conn, chief of emergency medicine, praised Boston’s EMTs for equitably spreading patients across the city and not deluging any trauma center with too many critical patients.

Bill Mergendahl, Chief Executive of Cambridge-based ProEMS, which sent six ambulances to the scene Monday in Boston, said his fleet transported patients with “traumatic amputations,” the medical term for the accidental severing of all or part of a body part.

“There was a lot of quick good work done by people first on the scene with tourniquets to stop bleeding before we got there, which was fortunate for the victims,” he said. Heavy blood loss can cause a condition known as hypovolemic shock, in which severe blood and fluid loss make the heart unable to pump enough blood into the body and cause organs to shut down.

The day after the bombings, “things were calmer” at Boston Medical Center and Dr. Tabbara visited with his young patient, who was able to speak and had been reunited with his family and friends.

He had facial swelling, but was in good condition, Dr. Tabbara said. He is unlikely to suffer brain damage, but there is the potential for nerve damage.

“He was grateful,” he said.

Dr. Tabbara says he is grateful, too, for some good news.

“This is a great city, it’s just a shame this happened,” Dr. Tabbara said,

Cambridge, May 15, 2015 — Cambridge Fire Department, along with PRO EMS of Cambridge, have jointly received the American Heart Association’s Mission: Lifeline®EMS Silver Award for implementing quality improvement measures for the treatment of patients who experience severe heart attacks.

When officers arrive to a medical emergency involving an overdose, it usually means the person is unconscious, according to Acton Police Department Sgt. Edward Lawton, a 22-year veteran of the department and a member of the its drug unit, formed in October 2012.